Vaccination has increased the average human lifespan worldwide more than 10 years during the 20th century. Breakthroughs in immunology, molecular biology and biochemistry in the last 25 years produced more than half of the vaccines used during the last 100 years. Despite this, little progress has been made in delivery since most are injectable and require strict maintenance of cold chain conditions.
Injectable vaccines have various drawbacks. Injections are the most common reason for iatrogenic pain in childhood and deter many from immunization. Injectable vaccines pose a significant risk to the safety of medical staff, patients and community. And most vaccines are unstable at ambient temperatures and require refrigeration.